One prime example of this, is carbohydrates.3 One of the three main macronutrients, carbohydrates, especially the simple, man-made kind, are no doubt 21st-cenury man’s favorite dietary indulgence.4, 5 Do you crave broccoli? Hard to resist kale? I didn’t think so.6, 7, 8
However, replace the words “broccoli” and “kale” with “Reese’s Pieces” and “M&Ms” and we have a different situation altogether.9 The combination of sugar and fat, in just the right proportion (known in the food chemist field as ‘the bliss point’) is nigh-impossible to resist – quite literally.10, 11, 12 But even without the processed food industry, our brain handles carbohydrates in a very unique way.13, 14
Carbohydrates are either simple or complex.15 Whether they fall into one camp or the other, depends on their chemical structure.16 Simple carbs have one to two sugars, while complex carbohydrates contain three or more.17, 18 The standard dietary recommendation calls for 40-60% of your daily calories to come from carbohydrates.19 However, this is not a good idea.20, 21, 22, 23, 24
Our brain function’s dependency on carbohydrates is variable.25 Serotonin-releasing brain neurons are unique in the amount of neurotransmitter they release is normally controlled by food intake: carbohydrate consumption – acting via insulin secretion and the “plasma tryptophan ratio” – increases serotonin release; protein intake lacks this effect.26
This accounts for the “boost” we get when consuming carbs – and why we turn to them, day after day, to “make ourselves feel better,” after a long stressful day at work.27 Besides, the oft-repeated, anecdotal phrase “carbs make us fat,” stands up to science.28 In one study, a carbohydrate-restricted diet resulted in a significant reduction in fat mass and a concomitant increase in lean body mass in normal-weight men.29 Researchers posit this may be due to the reduced circulating insulin.30
Yet, many of the guiding sources for suggested carbohydrate intake for adults are at odds.34 This suggests very low-carbohydrate diets may not only be sustainable, but they may indeed be optimal.35, 36 Researchers point the likely finger at decreased transport of glucose across the brain, instead replaced by ketone bodies.37, 38
In some individuals, this can help with mental and behavioral detriments, such as obsessive-compulsive disorder and schizophrenia.39, 40, 41 Since the original “very low carbohydrate” diets were developed for treating epilepsy, this should come as no surprise.42
After eating carbohydrates, the level of the amino acid tryptophan in the brain goes up.43 This rise in brain tryptophan level follows from an increase in tryptophan transport into the brain, the consequence of an insulin-induced reduction in the blood levels of several amino acids that compete with tryptophan for brain uptake.44 This helps to explain, at least partially, why you may feel sleepy after a meal filled with large amounts of carbohydrates.45
One, as yet, untouched problem with carbohydrates and your brain, is an increased risk for dementia.46 Glycation is a big problem, and as sugar binds to protein in your body, you are now at an increased risk for developing dementia.47, 48, 49 What can you do to help control this? Quite simply, lower your carbohydrate intake.50 Instead, eat a diet rich in healthy fats, high in quality protein, and with enough quality carbohydrates to maintain activity levels.51, 52, 53 Quite simply, eat a Paleo Diet.
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